The increase in antiretroviral use globally to treat HIV infections has been a much needed and worthy achievement as many thousands of lives have been saved by the rapid expansion of treatment. A natural byproduct of the increased use of these medications is the acquisition of drug resistance in patients failing therapy that will ultimately result in transmitted drug resistance. The timing of the increase in transmitted resistance, so that it impacts national antiretroviral therapy (ART) programs, is unclear, but in resource-limited regions, where it is not feasible to test all individuals for drug resistance at the time they enter care, alternative strategies to monitor resistance are needed. We hypothesize that transmitted drug resistance can be monitored with novel strategies in Botswana. In Specific Aim 1, we propose to conduct surveillance for transmitted HIV drug resistance in Botswana for four consecutive years using a surveillance method developed by the World Health Organization (WHO) in addition to our novel strategy of pooling samples and applying highly sensitive assays to detect drug resistance mutations critical to 1st line ART. This strategy will be validated by the standard genotyping results obtained by the WHO protocol. In Specific Aim 2, we restrict this method of pooling samples to only those individuals with recent HIV infection to see if this improves our ability to monitor transmitted drug resistance and also will closely evaluate transmission pairs to learn about the dynamics of transmission between partners. In Specific Aim 3, we will compare a pooling strategy to detect HIV drug resistance with a standard in-house genotyping technique to determine if this approach to genotyping provides meaningful, cost-effective, results prior to ART initiation. The data generated by this technique would again focus on those mutations relevant to 1st line ART to aid clinicians in predicting success of this therapy. The studies to be performed in this research will characterize the current state of transmitted drug resistance in Botswana by conventional and novel techniques and determine the feasibility of new strategies to monitor for the emergence of HIV drug resistance in resource-limited regions;essential components of monitoring to ensure the continued success of the ART program in Botswana. PUBLIC HEALTH RELEVANCE: Transmitted HIV drug resistance will undoubtedly increase in resource-limited regions as more antiretroviral therapy becomes available and this resistance will impact the success of national antiretroviral programs. The goals of this proposal are to: 1) Evaluate the extent of transmitted drug resistance in Botswana using the WHO recommended surveillance method in addition to a novel, less expensive approach that identifies those resistance mutations critical to 1st line antiretroviral therapy;2) To evaluate only those with recent HIV infection to enhance our ability to monitor transmitted drug resistance and to study the dynamics of viral transmission between partners;and 3) To assess if similar techniques can serve as a low cost alternative to genotyping prior to the initiation of antiretroviral treatment. These results will expand our knowledge about the current state of HIV drug resistance in Botswana and possibly provide less expensive strategies to monitor for resistance.